Metals

Question 1

Compare the general physical properties of metals and non-metals.

Answer 1

Thermal & electrical conductivity of metals good while nonmetals poor/none. Metals are malleable and ductile while non metals are brittle. Most of metals have high melting and boiling point while non metals are low.

Question 2

Describe the general chemical properties of metals, limited to their reactions with dilute acids?

Answer 2

Metals react with dilute acids will produce salt and hydrogen gas.

Question 3

Describe the general chemical properties of metals, limited to their reactions with cold water/steam?

Answer 3

Metals react with cold water/steam will produce metal hydroxide/metal oxide and hydrogen gas.

Question 4

Describe the general chemical properties of metals, limited to their reactions with oxygen?

Answer 4

Metals react with oxygen will produce metal oxide.

Question 5

Describe the uses of Aluminium in terms of their physical properties.

Answer 5

aluminium in the manufacture of aircraft because of its low density. aluminium in the manufacture of overhead electrical cables because of its low density and good electrical conductivity. Aluminium in food containers because of its resistance to corrosion.

Question 6

Describe the uses of Copper in terms of their physical properties.

Answer 6

copper in electrical wiring because of its good electrical conductivity and ductility.

Question 7

What is brass?

Answer 7

brass as a mixture of copper and zinc

Question 7

what is alloy?

Answer 7

An alloy is a mixture of a metal with other elements. Most alloys contain more than one metal. Some alloys contain non-metals. Alloys can be harder and stronger than the pure metals and are more useful.

Question 8

What is stainless steel?

Answer 8

stainless steel as a mixture of iron and other elements such as chromium, nickel and carbon

Question 9

Explain in terms of structure how alloys can be harder and stronger than the pure metals.

Answer 9

because the different sized atoms in alloys mean the layers can no longer slide over each other.

Question 10

Describe the uses of stainless steel in cutlery.

Answer 10

because of its hardness and resistance to rusting

Question 11

Identify representations of alloys from diagrams of structure

Answer 11

Draw both pure metals&alloys structure to compare.

Question 12

State the order of the reactivity series of metals.

Answer 12

potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, lead, hydrogen, copper, mercury, silver, gold

Question 13

Describe the reactions potassium with cold water.

Answer 13

potassium reacts violently with cold water to produce potassium hydroxide and hydrogen gas.

Question 14

Describe the reactions sodium with cold water.

Answer 14

sodium reacts quickly with cold water to produce sodium hydroxide and hydrogen gas.

Question 15

Describe the reactions calcium with cold water.

Answer 15

calcium reacts less strongly with cold water to produce calcium hydroxide and hydrogen gas.

Question 16

Describe the reaction magnesium with steam.

Answer 16

magnesium react with steam to produce magnesium oxide and hydrogen gas.

Question 17

Describe the reaction magnesium, zinc, iron, copper, silver and gold
with dilute hydrochloric acid

Answer 17

magnesium, zinc, iron, with dilute hydrochloric acid will produce salt and hydrogen gas, while copper, silver and gold with dilute hydrochloric acid no reaction because copper, silver and gold are less reactive than hydrogen in reactivity series.

Question 18

Deduce an order of reactivity from a given set of experimental results.

Answer 18

Usually table given, then you compare it.

Question 19

Describe the relative reactivities of metals in terms of their tendency to form positive ions, by displacement reactions, if any, with the aqueous
ions of magnesium, zinc, iron, copper and silver.

Answer 19

Usually table given, then you compare which one is more reactive will easier to form positive ions then replace another metals.

Question 20

Explain the apparent unreactivity of aluminium.

Answer 20

Alumuniun is a reactive metal, but it appears to be unreactive because Aluminium has an oxide coating that protects the metal from further corrosion. The oxide layer acts as a barrier, oxide layer also prevents other reagents from reacting with the Aluminium.

Question 21

State the conditions required for the rusting of iron and steel to form hydrated iron(III) oxide.

Answer 21

water and oxygen in air

Question 22

Explain how rusting of iron can be prevented and state & describe some common barrier methods, including painting, greasing and coating with plastic.

Answer 22

Rust can be prevented by coating iron with barriers that prevent the iron from coming into contact with water and oxygen. However, if the coatings are washed away or scratched, the iron is once again exposed to water and oxygen and will rust. Unlike some other metals, once iron begins to rust it will continue to corrode internally as rust is porous and allows both air and water to come into contact with fresh metal underneath any barrier surfaces that have been broken or scratched
Common barrier methods include: paint, oil, grease, and electroplating.

Question 23

Describe the use of zinc in galvanising as an example of a barrier method and sacrificial protection.

Answer 23

Galvanising is a process where the iron to be protected is coated with a layer of zinc. This can be done by electroplating or dipping it into molten zinc. ZnCO3 is formed when zinc reacts with oxygen and carbon dioxide in the air and protects the iron by the barrier method. If the coating is damaged or scratched, the iron is still protected from rusting by sacrificial protection.

Question 24

Explain sacrificial protection in terms of the reactivity series and in terms of electron loss.

Answer 24

Iron can be prevented from rusting using the reactivity series. A more reactive metal can be attached to a less reactive metal. The more reactive metal will oxidise and therefore corrode first, protecting the less reactive metal from corrosion. Zinc is more reactive than iron therefore will lose its electrons more easily than iron and is oxidised more easily. For continued protection, the zinc bars have to be replaced before they completely corrode.

Question 25

Describe the ease in obtaining metals from their ores, related to the position of the metal in the reactivity series.

Answer 25

Less reactive the metal, easier to extract them, More reactive the metal, hardest to extract them.

Question 26

Describe the extraction of iron from hematite in the blast furnace.

Answer 26

Iron is extracted in a large container called a blast furnace from its ore, hematite.
Modern blast furnaces produce approximately 10,000 tonnes of iron per day. The raw materials: iron ore (hematite), coke (an impure form of carbon) and limestone are added into the top of the blast furnace
Hot air is blown into the bottom.

Question 27

Describe the extraction of iron from hematite in the blast furnace, limited to :
(a) the burning of carbon (coke), including the word equation&chemical equation.

Answer 27

The burning of carbon (coke) to provide heat and produce carbon dioxide.
Coke burns in the hot air forming carbon dioxide.
The reaction is exothermic so it gives off heat, heating the furnace :
carbon + oxygen → carbon dioxide
C + O2 → CO2

Question 28

Describe the extraction of iron from hematite in
the blast furnace, limited to:
(b) the reduction of carbon dioxide to carbon
monoxide, including the word equation&chemical equation.

Answer 28

At the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide.
Carbon dioxide has been reduced to carbon monoxide.
carbon + carbon dioxide → carbon monoxide
C + CO2 → 2CO

Question 29

Describe the extraction of iron from hematite in the blast furnace, limited to:
(c) the reduction of iron(III) oxide by carbon monoxide.

Answer 29

Carbon monoxide reduces the iron(III) oxide in the iron ore to form iron. This will melt and collect at the bottom of the furnace, where it is tapped off.
iron(III) oxide + carbon monoxide → iron + carbon dioxide
Fe2O3 + 3CO → 2Fe + 3CO2

Question 30

Describe the extraction of iron from hematite in the blast furnace, limited to:
(d) the thermal decomposition of calcium carbonate / limestone to produce calcium oxide

Answer 30

Limestone (calcium carbonate) is added to the furnace to remove impurities in the ore. The calcium carbonate in the limestone thermally decomposes to form calcium oxide.
calcium carbonate → calcium oxide + carbon dioxide
CaCO3 → CaO + CO2

Question 31

Describe the extraction of iron from hematite in the blast furnace, limited to: (e) the formation of slag

Answer 31

The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate.
This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately
calcium oxide + silicon dioxide → calcium silicate
CaO + SiO2 → CaSiO3

Question 32

State that the main ore of aluminium is bauxite and that aluminium is extracted by electrolysis

Answer 32

Aluminium is a reactive metal, above carbon in the reactivity series
Its main ore, is bauxite, which contains aluminium oxide.
Aluminium is higher in the reactivity series than carbon, so it cannot be extracted by reduction using carbon
Instead, aluminium is extracted by electrolysis

Question 33

Describe the extraction of aluminium from purified bauxite / aluminium oxide, including:
(a) the role of cryolite

Answer 33

Bauxite is first purified to produce aluminium oxide, Al2O3.
Aluminium oxide is then dissolved in molten cryolite. This is because aluminium oxide has a melting point of over 2000 °C which would use a lot of energy and be very expensive
The resulting mixture has a lower melting point without interfering with the reaction. The mixture is placed in an electrolysis cell, made from steel, lined with graphite. The graphite lining acts as the negative electrode, with several large graphite blocks as the positive electrodes

Question 34

-Describe the extraction of aluminium from purified bauxite / aluminium oxide, including: (b) why the carbon anodes need to be regularly replaced

Answer 34

The carbon in the graphite anodes reacts with the oxygen produced to produce CO2.
C (s) + O2 (g) → CO2 (g)
As a result the anode wears away and has to be replaced regularly

Question 35

the reactions at the electrodes, including ionic half-equations.

Answer 35

At the cathode (negative electrode):
Aluminium ions gain electrons (reduction).
Molten aluminium forms at the bottom of the cell. The molten aluminium is siphoned off from time to time and fresh aluminium oxide is added to the cell
Al3+ + 3e- → Al

At the anode (positive electrode):
Oxide ions lose electrons (oxidation)
Oxygen is produced at the anode:
2O2- → O2 + 4e-

The overall equation for the reaction is:
2Al2O3 → 4Al + 3O2

A lot of electricity is required for this process of extraction, this is a major expense